實現 for 循環：如果值發生變化，做一些事情（即 make line）

Question

我有以下三個列表：

ov = [1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1]

participant = [1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 4, 4]

geom = ['0101000020E864000077C385FFB4231C417F437ECE83E95441', '0101000020E8640000F532AC46BA231C41A945335C84E95441', '0101000020E8640000CD138FFA46EA1A41C71D074C27E15441', '0101000020E864000087373742A94A1A41B6A39D38B0815441', '0101000020E86400003A60EE21A3231C41ACB8FFA584E95441', '0101000020E864000046717DBEB2231C4115840F5D84E95441', '0101000020E8640000AAAF4E36AB231C413AC5EB5D84E95441', '0101000020E8640000B84BD7B961231C41D245C83B85E95441', '0101000020E864000026940AB784231C417B5D79A984E95441', '0101000020E86400003FE809B587231C4102DB987E85E95441', '0101000020E8640000B8FC550A83231C41E5B0F93785E95441', '0101000020E8640000E1A849F9A1231C41009C21A684E95441', '0101000020E8640000E1A849F9A1231C41009C21A684E95441', '0101000020E864000066EB7C29A0231C41F29756A684E95441', '0101000020E86400009B3CC349DC711C41EE7E428C76E15441', '0101000020E86400008985282945681C4182B65E6F50DC5441', '0101000020E86400005B469B1AB1711C410553435A76E15441']

現在我想在以下條件下創建線條：

• 使用geom作為點，一條線通常在ov為1時開始，在ov為0時結束

• 除非參與者改變，然后新的一行開始

因此，在我的情況下，我想使用geom創建線串，其中ov為：

linestring 1: 1, 0
linestring 2: 1, 1, 1, 1, 1, 0
linestring 3: 1, 1, 1, 0
linestring 4: 1, 1, 1
linestring 5: 1, 1

我想使用 for 循環來做這個，但我不知道如何實現它說：如果值正在改變，那么停下來做一條線。

注意：問題不在於如何制作一行，而在於如何在實現中使用所有正確的值。

我希望我解釋得很好，有人可以幫助我，在此先感謝！

Answer 1

假設participant總是排序的，使用itertools.groupby根據其元素對項目進行分組：

for k, g in groupby(zip(participant, ov, geom), itemgetter(0)):
    # k: element of participant
    # g: all (participant, ov, geom) items corresponding to k

要打印每一行，請將(ov, geom)元素與g （迭代器）分開並用逗號連接：

# each (ov, geom) --> "ov, geom"
line = ', '.join(map(lambda x: str(x[1])+', '+x[2], g))

完整代碼：

from itertools import groupby
from operator import itemgetter

for k, g in groupby(zip(participant, ov, geom), itemgetter(0)):
    print('linestring %i:' % k, ', '.join(map(lambda x: '%s, %i' % x[1:], g)))

輸出：

linestring 1: 1, 0101000020E864000077C385FFB4231C417F437ECE83E95441, 0, 0101000020E8640000F532AC46BA231C41A945335C84E95441
linestring 2: 1, 0101000020E8640000CD138FFA46EA1A41C71D074C27E15441, 1, 0101000020E864000087373742A94A1A41B6A39D38B0815441, 1, 0101000020E86400003A60EE21A3231C41ACB8FFA584E95441, 1, 0101000020E864000046717DBEB2231C4115840F5D84E95441, 1, 0101000020E8640000AAAF4E36AB231C413AC5EB5D84E95441, 0, 0101000020E8640000B84BD7B961231C41D245C83B85E95441
linestring 3: 1, 0101000020E864000026940AB784231C417B5D79A984E95441, 1, 0101000020E86400003FE809B587231C4102DB987E85E95441, 1, 0101000020E8640000B8FC550A83231C41E5B0F93785E95441, 0, 0101000020E8640000E1A849F9A1231C41009C21A684E95441, 1, 0101000020E8640000E1A849F9A1231C41009C21A684E95441, 1, 0101000020E864000066EB7C29A0231C41F29756A684E95441, 1, 0101000020E86400009B3CC349DC711C41EE7E428C76E15441
linestring 4: 1, 0101000020E86400008985282945681C4182B65E6F50DC5441, 1, 0101000020E86400005B469B1AB1711C410553435A76E15441

為清楚起見，在單獨的行上打印每對項目：

linestring 1:
   1, 0101000020E864000077C385FFB4231C417F437ECE83E95441
   0, 0101000020E8640000F532AC46BA231C41A945335C84E95441
linestring 2:
   1, 0101000020E8640000CD138FFA46EA1A41C71D074C27E15441
   1, 0101000020E864000087373742A94A1A41B6A39D38B0815441
   1, 0101000020E86400003A60EE21A3231C41ACB8FFA584E95441
   1, 0101000020E864000046717DBEB2231C4115840F5D84E95441
   1, 0101000020E8640000AAAF4E36AB231C413AC5EB5D84E95441
   0, 0101000020E8640000B84BD7B961231C41D245C83B85E95441
linestring 3:
   1, 0101000020E864000026940AB784231C417B5D79A984E95441
   1, 0101000020E86400003FE809B587231C4102DB987E85E95441
   1, 0101000020E8640000B8FC550A83231C41E5B0F93785E95441
   0, 0101000020E8640000E1A849F9A1231C41009C21A684E95441
   1, 0101000020E8640000E1A849F9A1231C41009C21A684E95441
   1, 0101000020E864000066EB7C29A0231C41F29756A684E95441
   1, 0101000020E86400009B3CC349DC711C41EE7E428C76E15441
linestring 4:
   1, 0101000020E86400008985282945681C4182B65E6F50DC5441
   1, 0101000020E86400005B469B1AB1711C410553435A76E15441

Answer 2

您可以使用zip來組合 3 個列表。

entries = zip(ov,participant,geom)
for entry in entries:
    # for the first entry it should print 1,1,0101000020E864000077C385FFB4231C417F437ECE83E95441
    print(entry)